artificial knee

As a part of my course work in material sciences, I am writing a paper
on the kind of materials used in an artificial knee. Its more of

engineering stuff than medical. The info that I require is on the
properties of the material & why those materials only. The more
exhaustive the info the better. Kindly help me out on this one. Thank
You. Ameya

The exact materials involved in each step are subject to change simply
because bio and biocompatible materials are really hot areas of research
right now, but this example should help in terms of what to look for.
In the replacement, the end of the femur, patella and end of the tibia
are replaced due to cartilage damages, but I'll just give you an example
of the tibia part. It is a combination of polymer and metallic
components. The end of the tibia is replaced with a sort of baseplate
of porous tantalum (we are talking on the order of 80% porosity). In
the US, it must be cemented into the tibia. The surface of the
baseplate has to act like a cartilage surface so UHMW polyethylene is
compression molded into and above the porous metal. So what you end up
with is a sort of composite baseplate of porous metal and polymer. The
remaining porosity that hasn't been filled in with polymer acts like a
matrix to promote bone growth.
Specific materials aside, the goal is to not only reproduce the
functionality of each component part, but also allow for bone and tissue
regrowth (biocompatibility and growth design). When you find different
examples of materials you should also keep in mind what they look at in
terms of strength and fatigue. These parts really can't break or you
are putting the patient in severe danger.
Seth

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